The Quality Assurance Laboratory (QAL) in the Comparative Medicine Branch at the National Institute of Environmental Health Science (NIEHS)performs testing on the microbiological and/or chemical contamination of critical aspects of the overall NIEHS research program. Our primary task is monitoring the animal research program for microbiological and/or chemical contamination that may affect animal health and welfare, as well as, the physiological responses of animals used in research studies. Our research focuses on the physiological effects of natural or contaminating microorganisms or compounds in the micro-environment (e.g., animal feed, caging, bedding, water, etc.)of the research animals. Our goal is to assure that we minimize exposure to environmental compounds that may effect animal health and welfare or alter physiological responses of the animals resulting in unacceptable variability. Historically, QAL studies have focused on the potential for endocrine-disrupting compounds EDCs) being present in the micro-environment of the research animals and the impact these compounds may have on study outcomes, especially reproductive development. We have shown that natural phytoestrogens (e.g., daidzein and genistein) present in commercially available rodent diets or added to diets free of these compounds or the presence of the mycotoxin, zearalenone can accelerate reproductive development in juvenile female mice. The current studies being performed in QAL include the following: 1. The effects of topical application of Bentonite clay (Natural Green clay) on mice for the treatment of dermatitis and the natural contamination of the clay with arsenic and lead. 2. The effect on the gutl and lung bacterial microbiome and lung inflammatory transcriptome in mice after changes in the type of caging used to house mice. 3. Toxicogenetic profiling of Clostridium perfringens isolates from rodent feed.